1. Field of the Invention
This invention relates generally to circuitry for protecting an electrical circuit element from possible catastrophic damage during operation and more particularly to limiting circuitry for current in the magneto-resistive element of a magnetic read head in response to an abnormal operating condition such as a short circuit occurring in the element.
2. Description of Related Art
Apparatus for controlling the bias current in a magneto-resistive element utilized in a read head of a high performance hard disk drive differential preamplifier is generally known. Conventional approaches sometimes resort to fixed level limiting which wastes power consumption particularly when the bias current must be programmable over a wide range. However, such apparatus is not known to include means for limiting the current to a level which can prevent catastrophic damage when the element is shorted. Furthermore, limiting by means of shunting the excess current away requires large output devices and wastes unnecessary power.